Little is known about the causes of childhood cancers, but there has been increasing public concern that environmental toxicants may contribute to the risk of developing this heterogeneous group of diseases. California, with the largest population-based cancer registry in the world and with a unique wealth of environmental exposure databases, provides an unusual opportunity to evaluate these rare malignancies in geographically and socio-culturally diverse settings. The proposed study seeks to evaluate the first five years (1988-1992) of California statewide population-based childhood cancer incidence data in conjunction with geographic indicators of the socio-cultural diversity of the state, and in conjunction with well characterized and temporally relevant detailed statewide environmental exposure information, to explore some of the more prominent current hypotheses about environmental influences on the etiology of these diseases. This work is designed to build on the California Department of Health Services/Environmental Health Investigation Branch's long history of work in the study of childhood cancer "clusters", in characterizing environmental exposures of concern to human health, and in developing geographic information system (GIS) analysis strategies to complement epidemiologic research efforts. Specific aims are targeted at an evaluation of: - How childhood cancer rates vary with geographically defined environmental emissions or exposures; - How childhood cancer rates vary by demographic characteristics of the population; and - The independent effects of environmental or demographic risk associations. The proposed research is designed to identify risk associations worthy of more in-depth investigation, while minimizing some of the limitations of ecologic research. The investigators state that the availability of unique existing databases to characterize both exposure and disease outcome in California's large and heterogeneous population offer an opportunity to integrate epidemiologic, environmental exposure, and GIS analytic strategies to enhance our understanding of factors influencing a group of rare diseases which constitute a major cause of death in children.